The invention is based on a unit for delivering fuel from a supply tank to the internal combustion engine of a motor vehicle. German Offenlegungsschrift 33 035 709 discloses a delivery unit of this kind in which an electric drive motor and a feed pump driven to rotate by the motor are disposed in a common housing, which is connected on the suction side to the supply tank via a suction fitting and on the pressure side is connected via a pressure fitting to a feed line to the engine of a vehicle. The electric drive motor of the invention is embodied as an axial field motor, having a disk-shaped rotor part, guided on a shaft attached to the housing, that cooperates with permanent magnets disposed axially to it in a circle around the rotational axis of the rotor part. The rotary motion of the rotor part is transmitted to an impeller, which is embodied as the feed member of the feed pump and which is likewise guided on the shaft attached to the housing, which impeller aspirates the fuel via the suction fitting into a pump chamber, accelerates it, and supplies it to the pressure fitting at increased pressure. In order to be able to embody the measurements of the delivery unit as short as possible in the axial direction of the electric drive motor and feed pump, the rotor part and impeller have only a slight space between them or, as shown in FIGS. 9-12 of the cited patent disclosure document, are disposed occupying a common radial limiting plane.
The rotor part of the axial field motor and the impeller of the feed pump are combined in one disk-shaped element; involute-shaped feed fins, which have a curved course, are disposed on the face end of the rotor part and of the adjoining wall, which defines the pump chamber; during the rotating motion of the rotor, these feed fins feed fuel from a radially inner chamber to a radially outer chamber by increasing the pressure. The feed fins are constituted by means of conductor strips mounted on the rotor, which are charged via a commutator with an alternating, opposite electric potential. This commutator is embodied as a disk commutator, which is constituted by means of the radially internal part of the rotor; two commutator brushes, which are acted upon by differing electrical potential, are held in axial contact with one face end of the rotor by means of spring pressure.
The known fuel delivery unit has the disadvantage, though, that by means of the involute-shaped feed fins on the rotor part and on the face end chamber walls, it has a relatively complicated design, which results in a high cost of manufacture. Moreover, the feed pump reaches proper efficiency only at high speeds, which are connected to a high noise emission, so that it does not satisfy current requirements of a delivery unit for an internal combustion engine.